If you were suggesting a refrigerator to run the cooling in the night so much so that it'd be able to sustain a safe temperature for many hours while conserving energy in the day, then yes, you were suggesting making it so cold as to damage food - a few degrees difference isn't sufficient to achieve what you want, and if your temperature fluctuates more than 3-4 degrees then the food either gets unsafely warm or gets frozen/damaged.

I wasn't suggesting that, no.

I was just generally arguing against the parent proposition as well.

Well, if you're a skeptic as to how much can be saved, you might want to look at the many "smart grid" studies, because this has been a hot topic for a while and is already implemented to a small degree.